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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5423-5428 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoion and photoelectron yields were measured for poly(methylmethacrylate) in the photon energy region of 8–40 eV using synchrotron radiation. Further, the valence-band structure was investigated with ultraviolet photoelectron spectra and valence effective Hamiltonian calculations. A significant difference was observed between the photon energy dependencies of photoion and photoelectron yields. The threshold energy for photoion emission was found to be 10.5 eV, while that for photoelectron emission was 8.5 eV, indicating holes created near the valence-band top do not contribute to the ion emission. At the higher-energy region, the ion emission efficiency was found to be enhanced in the photon energy region of 17–28 eV. The difference between the threshold energies of photoion and photoelectron emission and the enhancement of the photoion emission are discussed in conjunction with the valence-band structure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 404-410 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We deposited polymer-like a-C:H films using the plasma-enhanced chemical vapor deposition technique and characterized film microstructure by variable-energy positron lifetime spectroscopy, photoluminescence (PL), and UV-visible absorption spectroscopy. It was confirmed that PL occurs from a chromophore in a sp2 cluster as a result of fast recombination of a photoexcited electron-hole pair. Positron annihilation lifetime spectroscopy showed that positronium (Ps) formation takes place via electron-positron recombination in the sp3 matrix. The lifetime of ortho-positronium (o-Ps) in our a-C:H films was similar to that in polyethylene, indicating their polymer-like nature. The relative PL efficiency increased by about an order of magnitude with increasing film band gap from 1.3 to 3.4 eV, which can be related to the decreasing concentration of nonradiative centers. On the other hand, Ps formation was much less influenced by the band gap and nonradiative centers. Comparison of this result with that for polyethylene mixed with carbon-black nanoparticles, where a considerable reduction in Ps formation was observed, showed that nonradiative centers were of a different nature from the defects on the carbon nanoparticle surface. This work demonstrated the usefulness of positron lifetime spectroscopy combined with optical measurements to study the nanostructure of a-C:H. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Inorganic chemistry 31 (1992), S. 4570-4574 
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 865-872 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Adhesion between thin Te-based alloy films and fluorocarbon polymer sublayers, prepared by sputtering or plasma polymerization, was investigated by observing the 1 μm-sized ablative hole opening process with a focused laser beam. Interpretations of the mechanisms for the change in energy required for the hole opening and pit geometry were based on the framework of studies of the ablative hole opening process for optical recording. Observations suggest that the molten material flow during the hole opening includes a ductile fracture and a viscous flow of the molten sublayer material as well as of active layer material. Adhesion acts as an energy barrier against the above mentioned flow of molten material during the hole opening process. Since the fluorocarbon films used in the present work had highly cross-linked structures, the adhesion was mainly dominated by the dynamic force of adhesion. Therefore, the hole opening process was mainly affected by the dynamic force of adhesion rather than the static force, which is dominated by the surface energy of the sublayer. There was a good correlation between the dynamic force of adhesion estimated by the peel-off strength and the concentrations of the -CF- and -C-CF- structures estimated from C1s spectra obtained by x-ray photoelectron spectroscopy. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic comparison of magnetoresistance, Hall effect, thermal conductivity, and thermoelectric power has been made on systems exhibiting giant magnetoresistance (GMR), Co/Cu/Ni(Fe) multilayers, and AgCo granular alloys, for examples. Each property exhibits field dependence characteristic of the GMR and justifies its own merit in characterizing the conduction-electron scattering responsible for the GMR. The comparison was extended to intermetallic compounds such as REGa2 and RECo2 (RE: rare earth element) which also show a large magnetoresistance.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5927-5932 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Comparison of the magnetoresistance (MR) on two groups of spin-valve multilayers, NiO/NiFe/Cu/NiFe/Cu/NiO and NiO/NiFe/Cu/NiFe/Cu, has been made in order to investigate the possibility of the enhanced specular scattering at NiO/metal interface. No clear difference in MR between the two systems has been found, suggesting that the enhancement of specular scattering at interfaces is not the origin of the large MR. For the field direction almost perpendicular to the plane, we found a sensitive angular dependence of MR along with a large unidirectional anisotropy. To sort out any specific characteristics of the spin-valve system compared to the multilayers, thermoelectric power and Hall effect have been investigated for the first time. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate the first room-temperature low-threshold continuous-wave (cw) operation of Al0.3Ga0.7As/GaAs single quantum well (SQW) heterostructure lasers grown by metalorganic chemical vapor deposition (MOCVD) on Si substrates using techniques of SiO2 back coating and thermal cycle annealing. The all-MOCVD-grown SQW lasers on GaAs/Si with etch pit density of 1.5× 107 cm−2 have threshold current as low as 55 mA (1.41 kA/cm2) under cw at room temperature. The SiO2 back coating is effective to obtain excellent current-voltage characteristics. Thermal cycle annealing is also found to improve the crystallinity of GaAs/Si and to contribute to room-temperature cw operation of the lasers on Si substrates.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1704-1706 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Positronium annihilation was applied to characterize the nanoporous structure of thin silicon oxide films sputter-deposited at different argon pressures ranging from 0.1 to 2.0 Pa. At higher argon pressures, the 3γ decay probability of ortho-positronium (o-Ps) was substantially enhanced. A comparison of this result with that obtained for capped samples indicated that: (a) 3γ annihilation is due to the intrinsic decay of o-Ps diffusing out from the film into vacuum and (b) films deposited at high argon pressures contain highly connected, open pores. Positron lifetime spectroscopy measurements on the capped films showed that the characteristic size of the pores can be as large as 2.6 nm, depending on the argon pressure. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2989-2993 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of LiNbO3 and LiTaO3 were grown on sapphire substrates by the rf-magnetron sputtering method. Structural characterization was made by several spectroscopic measurements: x-ray diffraction, Raman scattering, and optical absorption. We obtained epitaxial thin films with lattice-mismatched strained layers, without misfit defects which are usually created at the interface. Impurity-ion (Nd3+ and Cr3+) doped films were also grown; these films had larger refractive indices than the pure films. Furthermore, the heteroepitaxial thin films of up to 10 alternating LiNbO3/LiTaO3 layers were successfully grown, and their periodic structures were studied by optical second-harmonic generation.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 11 (1964), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Gross and microscopic radioautographic observations have been made on the sequential distribution of 32P in the brain and spinal cord of the dog after intracisternal injection as orthophosphate.There appear to be two stages in the process of 32P incorporation into central nervous tissues. In the first, the phosphate in the CSF penetrates the central nervous tissue by diffusion. In the second, the phosphate is incorporated into various organic compounds in response to metabolic processes.The chronological changes in intraneuronal 32P localization indicate incorporation into cellular protein, RNA, DNA, and lipid and depend upon the turnover rate of 32P in these fractions.In the metabolism of phosphate the molecular layer of the cerebellum probably is involved only in rapid changes reflected by the acid-soluble fraction. The cellular layers in addition are concerned with slower processes such as incorporation into structural compounds.
    Type of Medium: Electronic Resource
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